1. Technical Field
The present invention relates to an image formation device, such as a photocopier, a laser printer, a facsimile machine or the like, which utilizes an electrophotographic process.
2. Description of the Related Art
In an image formation device of a photocopier, laser printer, facsimile machine or the like that employs an electrophotography process, a toner image is formed at a photosensitive drum, this toner image is transferred to a recording sheet such as recording paper or the like, and an image is formed on the recording sheet by thermal fixing.
At such an image formation device, as a method for forming the image at the recording sheet, beside a method of direct transfer from the photosensitive drum to the recording sheet, there is a method which utilizes an intermediate transfer body, such as an intermediate transfer roller, an intermediate transfer belt or the like, and after initially transferring the toner image from the photosensitive body to the intermediate transfer body, subsequently transfers the toner image from the intermediate transfer body to the recording sheet.
In such transfer methods, a transfer member such as a transfer roller or the like is disposed to oppose an image-bearing member, such as the photosensitive drum, the intermediate transfer body or the like. A transfer electric field is formed at a rear face of the recording sheet by the transfer member, by applying charge (a bias voltage) of the opposite polarity to a static charge of the toner. Thus, the toner image is electrostatically transferred to a front face of the recording sheet.
In such image formation devices, various kinds of data are stored in storing means, this data is selectively read out, and processing for image formation is implemented.
For example, an image formation device has been proposed in which a plurality of image creation conditions are specified, adjustment values for color balance conditions are preparatorily stored in non-volatile storing means for each of the image creation conditions, the adjustment values for a color balance condition that is closest to the color balance condition of an original are read out from the non-volatile storing means, and an image creation process is implemented (see, for example, Japanese Patent No. 2,655,844).
Further, an image formation device has been proposed in which, when a power supply to a copier device is turned on, initial mode-setting means sets the copier device to a predetermined transfer process operation mode, and rewriting means changes, for example, information at information-preserving means from information which designates a second storage region to information which designates a first storage region. Thereafter, when there is input from mode-inputting means, input mode-setting means correspondingly specifies a change of a mode set at the copier device to the inputted mode. At the same time, one of the storage regions, which is designated by the information preserved by the information-preserving means, is overwritten. When the power supply to the copier device is turned off, a mode at the moment of turning the power off is preserved at the one storage region immediately after the power is turned off. Thereafter, if there is a reset instruction from mode reset-instructing means while the power is on, reset mode-setting means updates to set the copier device to the mode in the other storage region. Thus, an operator can automatically set the copier device to the mode of a previous session simply by inputting a reset instruction at the mode reset-instructing means. (See, for example, Japanese Patent No. 3,089,018.)
An image formation device has further been proposed in which, when jam-detecting means disposed on a transfer member path detects a jam, a jam signal is stored in a non-volatile memory, and when an image formation task is to be commenced after jam processing, bias of transferring means is switched to an opposite polarity in accordance with the signal in the non-volatile memory (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 3-100580).
Further still, a facsimile device has been proposed in which a past state of working of heating means is stored in storing means, and a state of working of the heating means is controlled on the basis of stored contents of the storing means (see, for example, JP-A No. 6-253120).
Now, when a toner image is formed at a recording sheet by electrostatic transfer, one factor which has a great effect on the electrostatic transfer of the toner (the toner image) is variations in a resistance value of the transfer member. Generally, with a conductive transfer member, the longer a duration of current flow, the higher the resistance value. The resistance value also becomes lower when temperature rises, and the resistance value is greatly altered by environmental conditions such as temperature, humidity and the like.
Furthermore, electrical characteristics of the recording sheet also have a great effect on the electrostatic transfer of toner. That is, a resistance value of the recording sheet is a factor which has a great effect on a transfer electric field.
In an image formation device, if the same bias voltage is applied even though the various factors that affect the transfer field have changed, an appropriate transfer field cannot be applied between the image-bearing member and the recording sheet, and transfer efficiency deteriorates. At such a time, a lowering of quality of the image that is formed on the recording sheet occurs.
Accordingly, a toner image transfer device has been proposed in which effect factor-detecting and -inputting means is provided. The effect factor-detecting and -inputting means detects and inputs factors that have effects on transfer of toner images. Initial transfer parameters, which are used for transfer of a toner image, are determined on the basis of values from this effect factor-detecting and -inputting means, and correction transfer parameters are specified on the basis of correction values which are inputted in order to correct the initial transfer parameters. A toner image on an image-bearing body is transferred to the recording sheet in accordance with the initial transfer parameters and the correction transfer parameters. See, for example, JP-A No. 2001-175089.
However, in image formation devices, not only common recording sheets such as ordinary paper, high-quality paper, recycled paper, transparencies and the like are used. Users can also select and use, for example, heavy papers, film-coated papers and the like. Even when different recording sheets are used by respective users in this manner, high-quality image formation is desired. In consequence, because the users have to input various parameters on each occasion of image formation, operations for image formation are more complicated, and high-quality images may not always be obtained.